Use of wax emulsions for improvement of wood durability ... - TARA

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Use of wax emulsions for improvement of
wood durability and sorption properties
Boštjan LESAR and Miha HUMAR*
University of Ljubljana, Biotechnical Faculty, Department for wood science and
technology
Jamnikarjeva 101, SI 1000 Ljubljana, Slovenia
miha.humar@bf.uni-lj.si
Abstract:
Waxes are used for treatment of wood surfaces for several decades predominately as surface
treatments because they weakly penetrate into the wood. In order to overcome this issue, water
emulsions were applied in the present experiment. Five water emulsions of various concentrations
were used, namely montan wax, polyethylene, ethylene copolymer and oxidized polyethylene wax.
Performance of wax treated beech (Fagus sylvatica) and Norway spruce (Picea abies) against
white rot, brown rot and blue stain fungi was tested. In parallel, sorption properties of wax treated
wood were determined. The treated specimens were more resistant to wood decay fungi.
Polyethylene and oxidized polyethylene wax were found to be particularly efficient. Although this
treatment does not improve resistance to blue stain fungi, it reduces the sorption of water.
Die Verwendung von Wachsemulsionen zur Verbesserung der
Dauerhaftigkeit und der Sorptionseigenschaften von Holz
Zusammenfassung
Seit Jahrzehnten werden Wachse fast ausschließlich zur Oberflächenbehandlung
von Holz verwendet, weil sie nur schwach in das Holz eindringen. Um das
Eindringverhalten zu verbessern, wurden in dieser Studie fünf verschiedene
Wasseremulsionen in unterschiedlichen Konzentrationen verwendet, und zwar
zwei Montanwachse, Polyethylen, Ethylen-Copolymer und oxidiertes
Polyethylenwachs. Die Resistenz von wachsbehandeltem Buchenholz (Fagus
sylvatica) und Fichtenholz (Picea abies) gegen Weißfäule-, Braunfäule- und
Bläuepilze wurde untersucht. Daneben wurden die Sorptionseigenschaften von
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wachsbehandeltem Holz bestimmt. Die behandelten Prüfkörper waren gegen Holz
zerstörende Pilze resistenter, wobei sich Polyethylen und oxidiertes
Polyethylenwachs als besonders wirksam erwiesen. Zwar wird mit dieser
Behandlung die Resistenz gegen Bläue nicht verbessert, jedoch wird die
Wasseraufnahme reduziert.
1. Introduction
Despite the fact that wood has been used for construction applications for
thousands of years, it remains one of the most important building materials. The
first users of wood faced the same problem that people face nowadays. Wood is
not durable in outdoors applications; therefore, it has to be protected in some way
if used in such environment. In the pa st, most preservative solutions had biocidal
properties and therefore, inhibited pest growth and development (Richardson
1993). Future solutions for the improvement of the durability of wood
preservatives are designed differently. They change the structure of wood so that
wood pests do not recognize it as food source (Tjeerdsma et al. 1998); or, wood
moisture content is kept so low that decay processes are no longer possible
(Goethals and Stevens 1994). It is believed that wax emulsions can be used in
such manner as well. Treatment of wood with resin/wax water-repellent
formulations greatly reduces the rate of water flow in the capillaries and
significantly increases the dimensional stability of specimens exposed to wet
conditions (Berninghausen et al. 2006, Kurt et al. 2008). The most important
applications of waxes in wood industry are found in particleboard production.
Paraffin emulsions are introduced to the particleboards reducing water uptake and
improving dimensional stability (Amthor 1972, Deppe and Ernst 1996).
Nowadays, wax emulsions are added to OSB boards for the same reason
(Neimsuwan et al. 2008). However, there are reports that paraffin treatment can
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reduce water capillary uptake in wood as well (Scholz et al. 2009). Furthermore,
wax treated wood exhibited increased compression strength and hardness (Rapp et
al. 2005). In addition, wax and oil emulsion additives are incorporated into
aqueous wood preservatives to reduce checking and improve the appearance of
treated wood exposed outdoors as well (Evans et al. 2009).
Montan and carnauba waxes are some of the possible water repellent agents to be
applied in order to improve wood durability as they are among the most resistant
waxes that form thin films. Montan and carnauba wax as well as other waxes are
almost non-toxic and are used for a variety of applications like for instance
cosmetics (Anonymus 2005). Crude montan wax belongs to the group of naturally
occurring waxes of vegetable origin such as carnauba wax or candelilla wax.
Montan wax is fossilized vegetable wax extracted from lignites, principally from
central German brown coal reserves west of the Elbe River. It is a mixture of
chemical compounds that can be divided into three substance groups: waxes,
resins, and asphaltic substances. Just like existing vegetable hard waxes such as
carnauba wax, the pure wax substance in montan wax consists mainly of esters of
long-chain acids with long-chain alcohols and free long-chain acids. Other
components such as free wax alcohols or ketones, paraffins or terpenes are usually
present in small quantities (Matthies 2001). Wax is soluble in many organic
solvents, particularly aromatic or chlorinated hydrocarbons, even under moderate
heating. Montan wax is used in the form of flakes, powders, pastes with solvents,
or aqueous emulsions (Heinrichs 2003). One of the most important advantages of
montan wax is its capability to form thin-layer resistant films (Warth 1959). One
of the objects of this study was to show that this thin film could limit water
penetration and as such improve performance against wood decay fungi. There are
also other waxes - beside montan wax - used for the protection of concrete against
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stains, particularly polyethylene, ethylene copolymer and oxidized polyethylene
wax. Some of those waxes are already being used for car and plastic polishing
(Erhuai 2008), as they protect the surface against salt, dust and other pollutants.
Another important application is the protection of concrete walls and facades
against weathering, staining etc. It is believed that they can form a film on the
wood surface as well as cell lumen. This enables faster water removal and
decreases water sorption and desorption which results in an improved dimensional
stability of wood. Dry wood will be less susceptible to fungal decay. Until now,
wax (bee and paraffin waxes) has predominately been used for surface coatings
(Burger 2006). It was dissolved in an organic solvent or melted prior use.
However, melted waxes are only of minor importance as they do not penetrate
deeper into the wood and remain on the surface of the treated material for most of
the treatments. A second treatment of wood with melted waxes requires special
equipment, it is expensive and there is an increased risk of fire (Scholz et al.
2009). On the other hand, organic solvents are becoming less and less desired due
to environmental issues. The authors` intention is to prepare wax emulsions which
will penetrate deeper into the wood and, therefore, protect it against fungal decay.
To the authors` knowledge nothing has been reported on wax use in the field of
wood protection.
2. Material and methods
Treatment solutions used
For impregnation, five types of wax emulsions of various concentrations were
used, namely two emulsions of montan wax (LGE, MW1), one emulsion of
polyethylene (WE1), one emulsion of ethylene copolymer (WE3) and one
emulsion of oxidized polyethylene (WE6) wax. The solutions are commercially
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available and produced by Samson (Slovenia) and BASF (Germany).
Concentrations (dry content) and basic properties of the wax emulsions can be
seen in Table 1. In order to elucidate the penetration of wax emulsions to wooden
specimens, the uptake of emulsions and the retention of waxes were determined
gravimetrically. For retention measurements, samples were dried at 103 °C for 24
hours, and their masses were determined before and after impregnation, and then
the retention was calculated. This gravimetrically determined retention of wax
was compared to the theoretical retention calculated from the uptake of solution
and the concentration of wax in the emulsion.
Wood decay test
Resistance of wood impregnated with various wax emulsions against wood decay
fungi was determined according to EN 113 procedure (EN 113:989). Specimens
were treated with various wax emulsions prior fungal exposure (vacuum – 70
mbar; 20 min; pressure – 9.5 bar; 60 min; vacuum – 70 mbar; 10 min), as can be
seen in Table 1. Wax treated specimens were air dried for four weeks. Steam
sterilized, impregnated and unimpregnated wood specimens were exposed to three
brown rot (Antrodia vaillantii, Serpula lacrymans and Gloeophyllum trabeum)
and three white rot fungi (Trametes versicolor, Pleurotus ostreatus and
Hypoxylon fragiforme). Beech wood (Fagus sylvatica) specimens were exposed to
white rot and Norway spruce (Picea abies) specimens to brown rot fungi. After 16
weeks of fungal exposure, specimens were isolated and mass losses were
gravimetrically determined and expressed in percentages.
Blue stain and moulds test
Scots pine (Pinus sylvestris) wood specimens were surface brushed with various
wax emulsions (Table 2). Their resistance was determined according to EN 152-1
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procedure (EN 152-1:1996). The uptake of wax emulsions was approximately
200 g/m 2 . After brushing, samples were left to dry for 3 weeks. Half of the
samples were exposed to blue stain fungi, while the other half was exposed to
moulds for 6 weeks according to the requirements of EN 152-1:1996.
Aureobasidium pullulans and Sclerophoma pithyophila were used to test blue
stain organisms. Fusarium solani, Gliocladium viride, Penicillium expynsum, and
Penicillium janthinellum were used for testing mould organisms. Resistance
against disfiguring fungi was estimated visually according to EN 152-1:1996.
Additionally, color change was determined as well and expressed in the CIELab
color system.
Sorption properties
Only LGE emulsion was used for the determination of sorption properties. There
were two types of tests performed to determine sorption properties. In the first
one, impregnated specimens were conditioned in water container or in a high
humidity chamber, and their masses were monitored. In the second set of
experiments, a tensiometer was used.
The first set of sorption experiments were performed on Norway spruce wood
specimens (1.5 × 2.5 × 5.0 cm³) with end sealed (epoxy coating) axial surfaces.
They were impregnated (vacuum – 70 mbar; 20 min; pressure – 9.5 bar; 60 min;
vacuum – 70 mbar; 10 min) with LGE emulsions of two different concentrations,
LGE 50 and LGE 100. After four weeks of air drying, specimens were oven dried
(40 °C) for three days. Afterwards, half of the specimens were transferred to the
chamber with a relative air humidity of 82%. The masses of the specimens were
monitored daily for six weeks. The second half of the specimens were immersed
in distilled water. The masses of the specimens were monitored for three weeks
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after predetermined periods shown in Figure 2. All moisture contents given are
based on dry mass with wax.
In the second part of experiments, Norway spruce wood specimens of the
following size 2.0 × 3.0 × 4.0 cm³ (T × R × A) were utilized. The measurements
were carried out at room temperature (20 °C) at a RH of 40 – 50% on a Krüss
Processor Tensiometer K100. Axial surfaces of the specimens were positioned
such that in contact with water, and afterwards their masses were measured
continuously for 200 s. Each curve in Figure 3 is an average value of 10
measurements.
3. Results and discussion
Wax emulsions used for impregnation in this experiment had different dry
contents. They varied between 5.3% (LGE 50) and 23.1% (MW1 50) (Table 2).
The influence of dry content on the properties of the emulsions, predominately
viscosity, is significant. However, viscosity is also influenced by other
parameters. The highest viscosity was observed for the WE3 emulsion, where a
considerably higher viscosity is reported compared to the other waxes with a
similar or even higher dry content. All emulsions applied, with the exemption of
LGE, have a rather high viscosity. Their penetration is presumably more limited
compared to the penetration of aqueous solutions. In general, no difference was
observed between the uptakes of preservative solution for beech wood specimens.
Those specimens in average retained 650 kg/m 3 of wax emulsions. However,
considerably higher variations in retentions were observed for spruce wood
specimens. Specimens impregnated with LGE 50 wax emulsion retained 570
kg/m 3 of emulsion, while parallel specimens that were treated with the WE6 50
emulsion up to 340 kg/m 3 of wax emulsion was retained (Table 2). It is presumed
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that the main reason for the observed effect could be a better impregnability of
beech wood compared to spruce wood. It seems that the ability to penetrate into
spruce wood specimens is in tight correlation with the dry content of wax
emulsions applied. For specimens that were impregnated with emulsions of
higher concentration, lower uptakes of preservative solutions were determined
than for parallel specimens preserved with emulsions with a lower dry content
(Figure 1). Although the emulsion particles (disperse phase) are rather small (100
nm), they are too big to penetrate into the cell wall. Lignified wood cell walls
contain a nanocapillary network that is 1 – 10 nm in size (Fujino and Itoh 1998).
Therefore, wax is deposited in the cell lumen only (Lesar et al. 2008).
The fact that particles in the emulsion are too big to penetrate into the cell wall is
reflected in the differences between gravimetrically determined wax retentions
and theoretical wax retentions calculated from the solution uptake and dry content
(Table 2). These differences varied between 2% and 23% in beech wood
specimens and between 12% and 74% in spruce specimens. This result shows a
better impregnability of beech wood. However, differences in retention are most
evident in spruce specimens impregnated with the WE3 emulsion, where 73% less
wax was determined than was presumed from the uptake of solutions. It is
presumed that during the impregnation process, water penetrated deeper into the
specimens while wax remained on the surface.
A more important object of this research was to determine the effect of wax
treatment on performance against wood decay fungi. All wood decay fungi used
in this experiment were vital, as mass losses of control specimens were higher
than 20%, with the exception of A. vaillantii where control specimens only lost
16.9%. This fungal strain is known as a less aggressive, but on the other hand very
effective degrader of impregnated and modified wood (Table 3).
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Mass losses of specimens impregnated with different wax emulsions varied from
2% (WE6 50; T. versicolor) up to 32% (WE3 50; H. fragiforme). As seen in Table
1, it can be concluded that applied wax emulsions can slow down wood fungi to
grow. Among the treatments the WE3 wax emulsion (emulsion of ethylene
copolymer wax) was found to be least effective. This emulsion was the most
viscose one among the emulsions tested, and its penetration into the wooden
specimens was the worst. It should be considered that most of the wax remained
on the surface of the treated specimens and therefore did not have prominent
influence on the performance of the impregnated wood (Table 2). Additionally,
specimens impregnated with montan wax emulsions (LGE and MW) were
decayed less than the control ones. Among the fungi tested, montan wax
emulsions were found to be the least effective ones against G. trabeum. During
the 16 weeks of exposure to the fungi mentioned above, the control specimens lost
35.7% while the specimens impregnated with montan wax emulsions lost between
26.1% and 15.8% depending on the concentration of montan wax in emulsions.
Specimens impregnated with emulsions of higher concentrations were better
protected against wood decay fungi than specimens impregnated with lower
concentrations of montan wax (Table 3). Among the tested wax emulsions,
emulsions WE1 (emulsion of polyethylene wax) and WE6 (emulsion of oxidized
polyethylene wax) proved to be the most effective agents for the protection of
wood against wood rotting fungi. For example, after 16 weeks of exposure to G.
trabeum, mass losses of spruce wood specimens impregnated with the WE1 50
emulsion were only 3.8% and 5.7% after exposure to S. lacrymans. This treatment
was effective against white rot species as well. P. ostreatus caused mass loss of
8.4%, while T. versicolor decayed only 3.9% of impregnated specimens (Table 3).
Unfortunately, WE1 and WE6 emulsions were not that effective against A.
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vaillantii and H. fragiforme. A comparison of the dry content data and mass losses
after fungal decay revealed that there is no statistically significant correlation
between those two parameters. This indicates that fungicidal properties of
impregnated wood depend more on the properties of wax than those of dry
content. pH is one of the mechanisms which could explain the efficacy of the wax
treated wood. Wood treated with wax emulsions WE1 and WE6 with pH around 9
exhibited a better performance against wood decay fungi than montan wax treated
wood. It is well known that fungi prefer slightly acidic substrates rather than
alkaline ones (Schmidt 2006). However, resistance of wax treated wood to wood
decay fungi cannot be explained by pH dependent mechanisms, as wax emulsion
WE3 has alkaline pH, but fungi can degrade WE3 treated wood to similar extent
to the LGE ones. The other mechanism that potentially improves the performance
of the wax treated wood against wood decay fungi is film/barrier formed in the
cell lumina and on the surface of the specimens. This barrier slows down
moisturizing, the diffusion of enzymes and degradation products between hyphen
and wood. It is presumed that this mechanism only slows down the degradation
processes and does not stop them. Therefore it is suggested that the EN 113 test
should be prolonged to overcome the influence of a slow down diffusion. This
experimental issue is overcome in long lasting field tests. The preliminary results
of the double layer field trial showed that after two and a half years of natural
exposure there is considerable decay at the control unimpregnated spruce wood
specimens. After eight months of exposure, the first fruiting bodies of the
Gloeophyllum sp. were noticed. On the other hand, there were no signs of decay
on the parallel spruce wood treated with LGE, WE1 or WE6 emulsions. This is
additional evidence that wax treated wood exhibits a better performance against
wood decay fungi than untreated wood. As already explained, the authors believe
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that the most important reason for improved performance of wax treated wood in
double layers is due to moisture relating effects. Moisture content of wax treated
wood was lower. Therefore they are les susceptible to decay.
Unfortunately, wax emulsions do not improve the resistance of wax treated wood
against blue stain and mould fungi. Both control and impregnated specimens were
completely stained after blue stain exposure as well as after exposure to moulds.
The surface of the specimens was covered with stains that covered more than 60%
of the surface (Table 4). Despite the fact that both specimens exposed to blue
stains and moulds were estimated with the same mark (3), the color change (ΔE)
that can be seen in Table 4 clearly shows that control specimens exposed to the
blue stain fungi were considerably darker than the ones exposed to mould fungi. A
similar effect can be observed for impregnated specimens as well. Unfortunately,
none of the wax emulsions improved the resistance of the treated wood against
staining organisms. A visual estimation showed some traces of inhibitory
properties. All wax emulsions, with the exception of WE3, slightly inhibit
moulding. This effect was not expressed for all specimens but only for some of
them. The effect of waxes against blue staining was even less prominent. The
color analysis of the wax treated specimens exposed to staining fungi showed an
even more negative influence of waxes on the resistance against staining. This
analysis showed that there might be fewer individual stains on the surface of the
specimens, and there was less surface covered with stains, but those stains were
darker than the stains on control specimens. There might be a better resistance of
wax treated wood observed if the specimens had been impregnated instead of
surface treated.
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The impregnation of spruce wood with waxes has an effect on sorption properties
of impregnated wood as well. An increase of the moisture content of the LGE
impregnated specimens was slower compared to the specimens conditioned in
humid air as well as the ones immersed in water. The moisture content (MC) of
wood impregnated with the LGE emulsion after 60 days of conditioning was also
lower than the MC of control specimens. It can be seen from Figure 2a that the
MC of LGE 100 impregnated specimens at RH of 80% was 12.1%, while an 15%
higher moisture content was observed for the control specimens after 60 days of
conditioning. The MC mentioned above was even reached after 18 days for
control specimens. It can be seen in Figure 2a that even after 60 days of
conditioning of specimens impregnated with the LGE 100 emulsion, they did not
reach their equilibrium moisture content. The MC of LGE treated specimens was
still slightly increasing even after two months of conditioning. This indicates that
the LGE wax can form a film on wood that is able to significantly slow down the
adsorption. A similar effect was observed during the wetting of wooden
specimens (Figure 2b). The uptake of water of specimens impregnated with LGE
emulsions was slower than that of control specimens. The final MC of control
specimens was 96%, while LGE impregnated specimens absorbed approximately
17% less water. It is presumed that there are three reasons for this. Firstly, waxing
makes the surface of the specimens more hydrophobic. Secondly, the cell lumina
were at least partly filled with waxes and this physically prevents moisturizing.
Finally, there were thin film-barriers formed on the surface of the wooden
specimens, which slow down water movement.
This hydrophobic effect of the montan wax can also be seen from the
measurement of the water uptake using tensiometer (Figure 3). During this test,
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axial surfaces of wooden specimens were positioned such that in contact with
water. Afterwards, the water uptake was gravimetrically measured. The uptake of
water in control spruce wood specimens was relatively fast. Within 200 s,
specimens from axial surfaces (6 cm 2 ) retained more than 0.8 g of water. The
shape of the uptake is clearly logarithmical. The uptake of water is faster in the
beginning and then slows down. Approximately half of the water was absorbed
after 30 s (Figure 3). The water uptake in the montan wax impregnated specimens
was considerably lower for both specimens impregnated with pure LGE emulsion
(LGE 100) and for the ones impregnated with the same emulsion of a lower
concentration (LGE 50). The shape of the water uptake curve for LGE treated
specimens significantly differs from the curve observed for control specimens.
The water uptake decreased during the initial stage. It reached its maximum after
12 s (LGE 100) or 16 s (LGE 50), and then appeared to decrease rapidly before it
started increasing again after 50 s (Figure 3). This pattern is characteristic for
hydrophobic surfaces (Rowel and Banks 1985). There was no decrease in the
water uptake, but this pattern is a result of the hydrophobic properties and the
lifting power of the water in contact with the surface where contact angles are
higher than 90 degrees. However, after 200 s the LGE 50 treated spruce
specimens took eight times less water up than the control ones, while the uptake
in LGE 100 treated wood was even lower. This is an additional proof that montan
wax treatment improves the sorption properties of wax treated wood.
4. Conclusion
The uptake of wax emulsion based solutions in spruce wood specimens was
influenced by dry content and viscosity of the wax emulsions applied. Some of the
wax emulsions tested do considerably slow down fungal degradation, but do not
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stop it. Emulsions of oxidized polyethylene wax (WE6) were found to be
particularly effective. Unfortunately, treatment of wood with waxes does not
prevent staining. One of the positive properties of treated wood is that the
impregnation of wood with emulsion of montan wax reduces water uptake of the
wax treated wood. It is believed that wax emulsions have the potential to be used
for wood protection in less hazardous outdoor applications.
5. Acknowledgements
The authors would like to acknowledge the Slovenian Research Agency for financial support in
the frame of the projects L4-0820-0481 and P4-0015-048. We appreciate the technical support of
Gregor Smrdelj, Žiga Melanšek and Jože Avguštinčič.
6. References
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EP1660285
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effective are they at improving the performance of preservative-treated wood? Forest Prod J. 59(1-
2): 66-70
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European Committee for Standardization EN 113 (1989). Wood preservatives; Determination of
the toxic values against wood destroying basidiomycetes cultured an agar medium
European Committee for standardization EN 152-1 (1996) Test methods for determining the
protective effectiveness of a preservative treatment against blue stain in service – Part 1: Brushing
procedure
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lignification of xylem cells in Eucalyptus tereticornis. Holzforschung 52: 111–116
Goethals P, Stevens M (1994) Dimensional stability and decay resistance of wood upon
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Heinrichs FL (2003) Montan wax. In: Bhonet M. (ed) Ullman’s encyclopedia of industrial
chemistry, Vol. 39 –chapter 3. Eds. Wiley-VCH, Weinheim, pp. 154-159.
Kurt R, Krause A, Militz H, Mai C (2008) Hydroxymethylated resorcinol (HMR) priming agent
for improved bondability of wax-treated wood. Holz Roh- Werkst. 66(5):333-338.
Lesar B, Zupančič M, Humar M (2008) Microscopic analysis of wood impregnated with aqueous
montan wax emulsion. LesWood 60(9): 320-326.
Matthies L. (2001) Natural montan wax and its raffinates. Eur J of Lipid Sci and Tech; 103:239-
248.
Neimsuwan T, Wang S, Via BK. (2008) Effect of processing parameters, resin, and wax loading
on water vapor sorption of wood strands. Wood Fiber Sci 40(4): 495-504
Rapp AO, Beringhausen C, Bollmus S, Brischke C, Frick T, Haas T, Sailer M, Welzbacher CR.
(2005) Hydrophobierung von Holz-Erfahrungen nach 7 Jahren Freilandtest. In: 24th
Holzschutztagung der DGFH, Leipzig, Germany, 157-170.
Richardson BA (1993) Wood Preservation. Second edition. E & FN Spon, London, Glasgow
Rowell RM, Banks WB (1985) Water Repellency and Dimensional Stability of Wood. Madison
U.S. Forest Products Laboratory. FPL 50-RP. pp. 24
Schmidt O. (2006) Wood and Tree Fungi Biology, Damage, Protection, and Use. Springer Berlin
Heidelberg, New York, pp. 329
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Soaked Scots Pine.in: 4 th European Conference on Wood Modification, Stockholm, pp. 209- 212
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Wood Preservation, Document, IRG/WP 98-40124, p. 10
Warth AH (1959) The chemistry and Technology of Waxes. Reinhold Publishing Corporation,
New York (USA)
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600
Uptake of wax emulsion (kg/m 3 )
550
500
450
400
350
r ²0.71
300
0 5 10 15 20 25
Dry content of emulsion (%)
Figure 1: Correlation between dry contents of the emulsion and uptake of
preservative solutions in spruce wood specimens
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14
12
a
10
MC (%)
8
6
4
2
0
control
LGE 50
LGE 100
0 10 20 30 40 50 60
Time (day)
120
100
b
80
MC (%)
60
40
20
0
control
LGE 50
LGE 100
0 100 200 300 400 500 600
Time (h)
Figure 2: Changes in moisture contents (MC) of the control specimens and
specimens treated with LGE wax emulsions in atmosphere with RH of 82% (a)
or during immersion in water (b).
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1,0
0,8
Control
LGE 50
LGE 100
Water uptake (g)
0,6
0,4
0,2
0,0
-0,2
0 50 100 150 200
Time (s)
Figure 3: Water uptake of axial surfaces of the montan wax (LGE) and control
specimens expressed in grams. Uptake was determined with tensiometer.
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Table 1: Selected properties of the undiluted/commercial wax emulsions used
Preservative
solution
Dry
content
(%)
pH
Emulsion
viscosity
(4 mm 23 °C)
ISO 2431
(s)
Density
(g/m 3 )
Melting
point of
solids (°C)
Average
particle
size (nm)
LGE 11.4 5.5 13 1.00 76 – 80 100 n.a.
Emulsifier system
MW1 46.2 4.6 25 1.01 78 100 Nonionic
WE1 36.4 9.9 20 – 36 1.00 130 – 135 100 Nonionic/anionic
WE3 28.4 9.7 85* 1.00 85 100 n.a.
WE6 38.2 8.9 20 – 60 1.00 126 – 133 100 Nonionic/anionic
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Table 2: Uptake of wax emulsions during impregnation process with regard to
concentration, wood species and composition of solution. In addition, there are
gravimetrically determined retention and differences between theoretically
calculated and actual retention.
Wax
emulsion
LGE
MW1
WE1
WE3
WE6
Spruce wood
Beech wood
Difference
Difference
between
between
Conc. Dry
Uptake of
Uptake of Retention theoretical
Retention theoretical
(%) cont. (%)
wax
wax emulsion of wax and actual
of wax and actual
(kg/m 3 ) (kg/m 3 emulsion
) wax
(kg/m 3 (kg/m 3 ) wax
)
retention
retention
(%)
(%)
50 5.3 555 26 12 644 34 2
100 11.4 386 32 27 647 67 10
25 10.9 441 41 16 639 58 17
50 23.1 347 53 34 662 126 18
25 9.4 500 39 16 641 56 6
50 18.2 370 52 24 668 113 7
25 7.3 569 30 29 659 40 17
50 14.2 494 18 74 663 72 23
25 9.4 462 35 19 655 56 9
50 19.1 340 45 31 670 110 14
20

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Wax
emulsion
LGE
MW1
WE1
WE3
WE6
Table 3: Mass loss of the wax treated spruce and beech wood specimens exposed
to various wood decay fungi according to EN 113 procedure.
Wood decay fungi
Conc.
(%)
G. trabeum A.
vaillantii
S. lacrymans P. ostreatus T.
versicolor
H. fragiforme
Mass loss (%)
50 26.1 11.2 18.8 15.2 24.6 28.5
100 24.7 14.8 17.8 11.4 20.4 23.7
25 22.2 10.4 17.2 13.2 21.4 24.4
50 15.8 11.7 13.1 7.3 13.9 20.7
25 6.0 7.3 12.2 14.8 20.8 30.9
50 3.8 10.9 5.7 8.4 3.9 18.3
25 21.2 16.1 27.4 13.7 30.6 27.6
50 13.6 16.2 30.0 20.4 22.3 32.4
25 23.0 11.3 7.1 10.0 17.9 22.4
50 7.7 7.8 3.2 8.9 1.6 21.7
Control / 35.7 16.9 40.2 23.0 32.0 32.7
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Table 4: Resistance of pine wood specimens to blue stain and mould fungi
determined according to EN 152-1 procedure.
Wax
emulsion
Conc.
(%)
Visual
estimation
-
moulds
Visual
estimation
-
blue stain
ΔE - Color change
after exposure to
moulds
ΔE - Color change after
exposure to blue stain
fungi
LGE 50 2.8 3 13.1 40.2
100 2.4 2.8 12.0 39.8
MW A 25 2.3 3 8.3 32.9
50 2.4 3 8.3 39.2
WE 1 A 25 2.4 3 11.1 29.2
50 2.9 2.6 12.2 21.1
WE 3 A 25 3 2.8 18.1 27.7
50 3 3 18.6 41.6
WE 6 A 25 2.6 2.6 12.0 32.9
50 2.25 3 27.2 32.3
Control / 3 3 9.1 25.9
22

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Abb. 1
Korrelation zwischen Trockengehalt der Emulsion und Schutzmittelaufnahme in
Fichtenholzprüfkörpern
Abb. 2
Änderung der Holzfeuchte (MC) der Kontrollproben und der mit LGE
Wachsemulsionen behandelten Prüfkörper a) in einer Umgebung von 82% rel.Lf.
oder b) bei Wasserlagerung
Abb. 3
Wasseraufnahme über die Hirnholzflächen von mit Montanwachs (LGE)
behandelten sowie Kontrollproben, in Gramm. Die Wasseraufnahme wurde mit
einem Tensiometer gemessen.
Tabelle 1
Verschiedene Eigenschaften der verwendeten unverdünnten/handelsüblichen
Wachsemulsionen
Tabelle 2
Aufnahme von Wachsemulsionen während der Imprägnierung in Abhängigkeit
von der Konzentration, der Holzart und der Zusammensetzung der Lösung.
Zusätzlich sind die gravimetrisch bestimmte Einbringmenge sowie die
Unterschiede zwischen theoretisch berechneter und tatsächlicher Einbringmenge
angegeben.
Tabelle 3
Masseverluste der wachsbehandelten Fichten- und Buchenholzprüfkörper nach
Befall mit verschiedenen Holz zerstörenden Pilzen gemäß EN 113.
Tabelle 4
Resistenz der Kiefernholzprüfkörper gegen Bläue und Schimmelpilze gemäß EN
152-1 bestimmt
23